Thermal relay



W. K. BECK THERMAL RELAY Feb. 24, 1970 2 Sheets-Sheet 2 -Filed Oct. 25. 1967 A 4 INVENTOR.

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United States Patent 3,497,853 THERMAL RELAY Willi K. Beck, Ann Arbor, Mich., assignor to King-Seeley Thermos Co., Ann Arbor, Mich., a corporation of Michigan Filed Oct. 25, 1967, Ser. No. 677,972 Int. Cl. H01h 37/46 US. Cl. 337-382 8 Claims ABSTRACT OF THE DISCLOSURE A thermal relay of the type which may be utilized to control high current rated circuits wherein the controlling contacts are actuated in response to the movement of a heated beam, the beam being heated either by self heating principles or by means of a heater coil wound in thermal communication therewith. Also, an eccentrically mounted head and shaft assembly is rotatably supported relative to a base member and is utilized to1 adjustably calibrate the operating point of the thermal re ay.

The purpose of the foregoing abstract is to enable the Patent Oflice and the public generally, and especially the scientists, engineers or practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

BACKGROUND AND SUMMARY OF THE INVENTION This invention generally relates to a thermally actuated relay assembly and more particularly to a thermal relay assembly having the controlling contacts actuated by means of a heated beam.

In certain applications, as for example in controlling the heating power of an oven, it has been the practice to utilize either hot wire or bimetal relays to control the oven heater units and thus control the enviromental temperature of the oven. However, with the advent of electric self clean ovens, with its attendant power requirements, it has been found necessary to improve the control relay, particularly for the high heat range of operation of the ovens.

With the relay of the present invention, the large mechanical power output required to control high currents and minimize contact arcing and thus contact deterioration is provided. Also, the system of the present invention necessitates the application of a very low heat in order to effect the necessary control of the movable member and ultimately the movable contact.

Accordingly, it is one object of the present invention to provide an improved thermal relay.

It is still another object of the present invention to provide a thermal relay having relatively large mechanical output capabilities.

Another object of the present invention is to provide a. thermal relay having improved high power control capabilities.

It is another object of the present invention to provide an improved thermal relay requiring a relatively low heat level to control the movable member thereof.

It is still another object of the present invention to provide a thermal relay having minimal thermal inertia.

It is still a further object of the present invention to provide a thermal relay having improved calibration characteristics.

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It is still another object of the present invention to provide an improved thermal relay which is reliable in operation and inexpensive to manufacture.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawings in which:

FIGURE 1 is a plan view of a thermal relay incorporating certain features of the present invention;

FIGURE 2 is a side view of the thermal relay of FIG- URE 1;

FIGURE 3 is an end view of the thermal relay of FIGURE 1;

FIGURE 4 is a bottom view of the thermal relay of FIGURE 1 and particularly illustrating a capacitor attached to certain terminals thereof;

FIGURE 5 is a sectional view of FIGURE 1 taken along line 5-5 thereof;

FIGURE 6 is another sectional view of FIGURE 1 taken along line 6-6 thereof; and

FIGURE 7 is still another sectional view of the thermal relay of FIGURE 1 as taken along line 77 thereof.

Referring now to the drawings, there is illustrated a thermal relay 10 which generally includes a base member 12 for supporting a calibration and support assembly 14. The support assembly is adapted to movably support a movable contact blade assembly 16 and a thermally actuated heated beam assembly 18. In opening the thermal relay, the position of the blade assembly 16 is initially adjusted by means of the assembly 14 as to its spacing from the base member 12 and subsequent heating of the heater assembly causes a blade associated therewith to elongate and thus move the support as sembly 16 towards the base. In this manner, a plurality on contacts, one pair of which is supported on the base 12 and the other mating pair of which is supported on the blade assembly 16, are actuated to control an external circuit in accordance with the degree of heat generation in the blade assembly 18. The external circuit, in the preferred embodiment, may include an oven heater which is selectively operated in the cooking range or in the self clean range.

The base member 12 may be fabricated form any suitable electrical insulating material which may be easily molded, as for example Steatite. The base member is formed with a generally fiat portion 24 having, integrally molded therewith, a raised portion 26 adapted to support the calibration assembly 14. Second and third portions 28, 30 are also integrally formed with the base 24 and are adapted to support a pair of input terminal assemblies 34, 36. The input terminal assemblies 34, 36 are utilized in energizing the heater coil of the heated beam assembly 18. The base member 24 is also formed with suitable apertures and slots to permit the mounting of a plurality of terminals 40, 42, 44, 46 and 48, the terminals 42, 44 being part of assemblies 34, 36 to provide electrical energy to the heater windings and the terminals 40, 46, 48 providing a controllable output current from the relay assembly 10.

The support assembly 16 includes a spring arm 50 having one end fixed to the base 12 by means of a pair of rivets 52, 54. The spring arm 50 includes a first extension 58 for supporting a first movable contact 60 and a second extension 62 for supporting a second movable contact 64. The central portion of the spring support 50 is provided with a certain degree of rigidity by means of a rigidizing plate member 70 which is suitably attached to the spring arm 50 by means of a rivet 72 and a pair of bent-over tab portions 74, 76. The tab portions 74, 76 are struck from the rigidizing member 70 and bent over the spring arm 50 after passing through a pair of apertures 80, 82. The sides of the rigidizing member 50 may also be bent at 84 to rovide further rigidizing for the spring arm 50.

Contacts 60, 64 are positioned in mating engagement with a second pair of contacts 90, 92, the contact 90 being connected to the output terminal 46 and the contact 92 being connected to the output terminal 48. Terminals 46 and 48 are suitably connected to the base member 12 by means of rivets 94, 96. Accordingly, the mating of contacts 60, 90 and 64, 92 permits current to flow through the spring support member 50 to the output terminal 40, the contacts 60, 90 and 64, 92 controlling the flow of current through this circuit. The contacts may also be utilized to control a circuit connected to a second terminal attached to the base by means of rivet 52 and extending through the aperture shown to the left of the rivet 52 (FIGURE 7), or to control the flow of current between terminals 46 and 48 and not utilizing terminal 40, or to control the current flowing through the relay with the input connected to terminals 46 and 48 and the output being taken at terminal 40 and the aforementioned second terminal.

The position of the spring support member 50, and thus the condition of the contacts 60, 64, is controlled by means of the heater-beam assembly 18, this latter assembly including a beam member 100 which is attached at one end thereof to the calibration assembly 14 by means of a tab portion 102 suitably welded thereto. The other end of the beam 100 is connected to the spring support member 50 by means of a tab portion 104 and the rivet 72. The tab 102 is connected to the calibration assembly 14, this latter assembly 14 including a connector element 108 which is welded or soldered to the tab 102, the member 108 including an eccentric aperture 110 which is adapted to receive an adjusting cam nut 112. The member 108 is also positioned relative to the base member by a guide 109 which surrounds the member 108 on three sides in the plane defined by the member 108. The adjusting cam nut 112 forms a fixed axis through a rivet 114 which passes through the eccentric nut 112, the connector portion 108 and an aperture 116 formed in one end of the spring arm member 50, as best seen in FIGURE 5.

It is thus seen that the end of support arm 50 is rigidly fixed relative to the base by means of the rivet 114 and the connecting member 108 and thus the tab portion 102 is moved toward and away from the fixed axis formed by rivet 114 in response to the turning of the cam nut 112. The movement of tab portion 102 either compresses or relaxes the main portion of the beam 100 to adjustably move the contact support spring member 50, and thus the contacts 60, 64, relative to the fixed contacts 90, 92.

The heat required to elongate the beam 100 is supplied by means of a heater element 120 wrapped in close thermal relation to the beam 100. Electrical energy is supplied to the heater 120 by means of a connecting wire 122 connected to the terminal 42 and a second connecting wire 124 connected to the terminal 44, these wires 122, 124 being physically supported by means of members 126, 128, respectively. Accordingly, when electrical energy is sup plied to terminals 42, 44, the heater 120 supplies heat to the beam 100 to cause the beam 100 to elongate. This elongation causes the closing of pairs of contacts 60, 90 and 64, 92 to start the flow of current between terminal 46 and terminal 40 and between terminal 48 and terminal 40. Thus the load connected toterminals 46, 48 is supplied with electrical energy.

The heater assembly 18 is a laminate type structure including the beam 100 and a pair of insulator members 132, 134 disposed on either side of the beam 100. Thus, with the heating of the beam 100 by means of the heater 120, the beam 100 is caused to elongate to close the contacts 60, 90 and 64, 92. Also, the deenergization of the heater 120 causes the opening of the contacts. A capacitor 138 is illustrated as being connected in parallel with the heater 120, and it is also to be understood that the capacitor 138 may be connected in series. The capacitor 138 is provided to improve the contact action of the mating contacts of a controller connected to control the heating of beam and is utilized to substantially reduce the contact arcing and welding of the controller contacts.

In operation, the relay 10 is connected in series with a pair of loads, as for example a bake heater connected to terminal 46 and a broil heater connected to terminal 48, or vice versa, with the relay 10 in series between the source of electrical energy and the load heaters. The relay 10 is adapted to be utilized in conjunction with a controller, as for example the controller disclosed in copending application Ser. No. 678,030, filed Oct. 26, 1967, in the name of Willi K. Beck and assigned to the same assignee.

When the heater is energized, the beam 100 will be elongated to cause the downward movement of the spring support member 50 in a direction toward the base member 12. Upon a sufficient movement of the spring support member 50, the contacts 60, 90 and 64, 92 will be in mating engagement to energize the load connected to the terminals 46, 48. A senser may be provided in the environment to be heated and provide a controlling signal to the relay heater 120 through the controller mentioned above. Thus, when the environmental temperature reaches a preselected set temperature, the circuit to the heater windin-g 120 will be broken to cause the deenergization of the heater winding 120. After sufficient cooling of the beam 100, the contacts 64, 92 will be open to deenergize the load connected thereto.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A thermal relay for controlling the flow of electrical energy comprising a base, a fixed contact supported relative to said base, a movable contact, support means fixedly supported relative to said base, a movable contact, support means fixedly supported relative to said base, and having first and second spaced legs and a crossmember attached to the ends of said legs opposite the fixedly supported end said movable contact being supported on said support means adjacent saidends of said legs for movement relative to said fixed contact in response to movement of said support means, and actuating means connected to said support means operable to control the movement of said support means and the position of said movable contact relative to said fixed contact, said actuating means including heated beam means for enhancing the mechanical output of said relay and decreasing the thermal inertia, said heated beam means including a thermally responsive heated beam fixedly supported at one end thereof relative to said base and at the other end thereof relative to said cross member of said support means, said heated beam being formed as a thin, fiat member, having minimal weight and maximal surface area and capable of bending upon elongation of said beam, said heated beam being in compression when cool and elongating and contracting in response to the application of heat thereto, said elongation and contraction controlling the movement of said support means by exterting a lateral and transverse force on said crossmember relative to said fixed end to move said cross-member in a direction parallel to said transverse force.

2. A thermal relay for controlling the flow of electrical energy comprising a base, a fixed contact supported relative to said base, a movable contact, support means fixedly supported relative to said base including a first leg extending generally in a direction from said fixed support toward said movable contact and a second leg extension generally perpendicular to said first leg, said movable contact being supported on said support means for movement relative to said fixed contact in response to movement of said support means, and actuating means connected to said support means operable to control the movement of said support means and the position of said movable contact relative to said fixed contact, said actuating means including heated beam means for enhancing the mechanical output of said relay and decreasing the thermal inertia, said heated beam means including a thermally responsive heated beam fixedly supported at one end thereof relative to said base and at the other end thereof relative to said second leg of said support means, said heated beam being formed as a thin, flat member, having minimal weight and maximal surface area and capable of bending upon elongation of said beam, said heated beam being in compression when cool and elongating and contracting in response to the application of heat thereto, said elongation and contraction controlling the movement of said support means by exerting a lateral and transverse force on said second leg relative to said fixed end to move said second leg in a direction parallel to said transverse force.

3. The relay of claim 2 wherein said heated beam means further includes heating means for supplying heat to said beam.

4. The relay of claim 3 wherein said heating means is a separate heater positioned in thermal transfer relation to said heated beam.

5, The relay of claim 1 further including an adjusting assembly and wherein said heated beam is connected to said base by means of said adjusting assembly.

6. The relay of claim 5 wherein said heated beam is connected in compression between said base and said support means during at least a portion of the operation of said relay.

7. The relay of claim 6 wherein said adjusting assembly is actuable to adjust the compression of said heated beam to adjust the response of said support means.

8. The relay of claim 5 wherein said adjusting assembly includes an annular member mounted relative to said base member for eccentric movement relative thereto, said eccentric movement adjusting the connection of said heated beam relative to said base.

References Cited UNITED STATES PATENTS 1,315,603 9/191-9 Geissinger 337392 2,312,974 3/ 1943 Owens. 2,412,483 12/1946 Warrington. 3,076,881 2/1963 Bastian. 3,176,099 3/ 1965 Bergsma. 3,193,648 7/1965 DeFalco. 3,270,167 8/ 1966 Broekhuysen.

BERNARD A. GILHEANY, Primary Examiner R. L. COHRS, Assistant Examiner US. Cl. X.R. 337-392 

